Micro total analysis systems (μTAS) are becoming more widely used, and further still more features are built into such systems. The systems may be used for fast analysis of small volumes of fluids. The micro systems comprise microfluidic channels and reaction chambers and also functional elements such as mixers, pumps and separation may be integrated on the chip. The detection of properties of fluids or fluid components is dominated by optical methods, such as fluorescence detection or absorption spectroscopy.
Typically, the optical systems are provided at a separate device or only partly integrated with the fluid handling system. There has been a strong effort to integrate parts of the optical system, such as waveguides with the fluid handling system, so that light may be provided to the sample to be analyzed and the resulting light, the sample light, resulting from the interaction between the incident light and the sample may be re-collected via integrated waveguides.
However, connection to external or off-chip active optical elements, such as light sources, detectors, spectroscopes, etc. is usually a demanding task, requiring precise alignment between the fluid handling chips and e.g. optical fibers connecting chip with the off-chip optical elements. The lack of precise alignment may result in loss of too much signal light to be able to practically detect the often weak optical responses from the sample.
Sample detection can be done using a wide variety of detection methods, and often a spectroscopic method is used. The spectroscopic methods may include simple fluorescence measurements, conventional absorption spectroscopy and advanced laser spectroscopy methods.